Dienals



United States Patent ()filice 3,189,655 Patented June 15, 1965 3,189,655DENALS Benjamin Thompson, Box 511, Kingsport, Tenn. No Drawing. FiledDec. 22, 1961, Ser. No. 161,352 19 Claims. (Cl. 260601) This inventionrelates to diene \aldehydes and to a process for making them. Morespecifically, it relates to unsubstituted 3,4-dienals and2-alkyl-3,4-diena1s and their conjugated isomers and the vapor phasepreparation thereof from acetylenic alcohol acetals of straight-chainaldehydes and aldehydes having at least one a-hydrogen.

In my co-pending application, Serial No. 75,475, filed December 13,1960, I have disclosed the synthesis of 3,4- dienaldehydes, hereinaftercalled dienals, of the formula wherein R R R R and R are hydrogen,alkyl, cycloalkyl or alkenyl. I have now discovered a new vaporphasemethod which provides an improved way of preparing such compounds,particularly those 3,4-dienals prepared from aldehydes having no or onlyone substituent group in the 2 position. Heretofore the greater activityof the single hydrogen-atom remaining after a straightchain aldehydehaving no substitution in the.2 position is reacted with the acetylenicalcohol has sometimes caused a further reaction which may consume someof the 3,4- dienal product. For example, for propionaldehyde in theliquid phase reaction there may be less opportunity for the allenicaldehyde formed to accumulate due to the reactive (ac-hydrogen remainingwhich apparently results in the formation of 2,2-diallenylpropionaldehyde. With so many reactive groups present, this product canbe rapidly lost by what may well be further condensation reactions.

Accordingly, it is an object of this invention to provide an improvedvapor-phase process for the preparation of unsubstituted 3,4-dienals and2-'alkyI-3,4-dienals as well as 2,2-substituted 3,4-dienals andconjugated dienals formed from them by isomerization or a shift of adouble bond. Another object is to provide a novel one-step vapor phasecatalytic process for the production of 3,4- dienals from acetylenicacetals prepared from straightchain aldehydes or aldehydes having atleast one a-hydrogen. Other objects will appear hereinafter.

I have now found surprisingly that dienals of the aboverecited formulaand 2,4-diene isomers thereof whereinone or both of R and R are hydrogenmay be prepared by an improved method in Whichacetylenic alcohol acetalsof straight-chain aldehydes or 'aldehydes having at least one a-hydrogenare contacted in the vapor phase in the presence of a metal-containingcatalyst, preferably a molybdenum oxide. Where the product is2,2-dialkyl substituted, 3,4-dienaldehydes are the major product. 3,5-dienals may be a minor product where the fifth carbon is disubstituted.On the other hand, where the product is unsubstituted ormono-substituted in the 2 position, considerable amounts of the3,5-dienal may be isomerized to the conjugated 2,4dienaldehydes,especially upon prolonged contact time or increased temperature.

By a metal-containing catalyst I mean a metal, metal oxide, metal salt,:or metal complex catalyst which may be supported on a suitable carrier,for example, an aluminum silicate, an active carbon, bauxite, asbestosor the like. The metal salt may be one that decomposes, such as thenitrate or oxalate or a salt from an acid that will pro-' vide an acidictype complex such as sulphate, phosphate, silicate or the like. Thecomplexes may be prepared by precipitating a mixture of the salts of themetals on a suitable carrier and then heating in a reducing atmosphereinitially. Preferred metal-containing catalysts include the metals andmetal oxides of Groups I and II of the Mendeleev Periodic Table wherethe metals have an atomic number of at least 29 and of Groups V throughVIII of the Mendeleev Periodic Table, mixtures of the preceding metals,mixtures of the preceding metal oxides, and mixtures of the specificmetals and metal oxides of said groups I and II and V through VllIclassification. Representative catalysts that may be used includecopperzinc, silver-zinc, and silver-zinc mixtures and complexes,silver-zinc or tin complexes, and the following metals or oxides, salts,mixtures or complexes thereof: vanadium, chromium, tin, copper, zinc,silver manganese, iron, cobalt, nickel, tungsten, platinum and the like.In my preferred embodiment the catalyst is a molybdenum oxide(principally -Mo O but not excluding M00) or a supported molybdenumoxide.

By acetylenicalcohol acetals I mean acetals of the formula R R 3H0 R5 R40-(2-CEC-R which are prepared from a propargyl alcohol or substitutedpropargyl alcohol of the formula wherein R R and R are alkyl,cycloalkyl, joined lower alkylene which with the carbon atom to whichthey are attached form a carbocyclic ring, e.g., as in cyclopentanolsand cyclohexanols having an acetylenic substituent in the 1-position oralkenyl as in the aforementioned dienal formula. Acetylenic alcoholsthat may be used include propargyl alcohol, 3-methyl-l-pentyn-3-ol,3-methyl-1- butyln-3-ol, 1-hex u1-3-ol, 4-ethyl-1-octyn-3-ol, 3-methy1l-nonyne-3-ol, l-ethynyl cyclohexanol, l-ethynylcyclopentanol,2,2,6-trimethyl-l-ethynycyclohexanol, and the like. The term propargylalcohol as used herein includes substituted propargyl alcohols.

The acetals which may be cracked according to my process may be producedby reacting a straight-chain aldehyde or an aldehyde having at least onewhydrogen, i.e., an aldehyde of the formula, R R CHCHO, with anacetylenic alcohol such as just described in the presence of an acidiccatalyst. Suitable aldehydes include: acetaldehyde, propionaldehyde,butyraldehyde, valeraldehyde, 3-methyl-pentanaldehyde, paraldehyde,n-butylaldehyde, isobutyraldehyde, Z-methyl-pentanaldehyde,Z-methylbutylaldehyde, 2-ethylbuytraldehyde, Z-methylhexanaldehyde,2-ethylhexanaldehyde, and the like.

Operating ranges for the improved process of this invention include acracking temperature range of ZOO-400 C., the preferred temperaturerange being from about 250 C. toabout 350 C., a pressure of from a mildvacuum to about p.s.i.g., preferably essentially atmospheric, and acontact time of up to about one minute, preferably from about 1 to 10seconds. Contact time is defined as the time in seconds that the gaseousfeed is in contact with the catalyst at reaction conditions oftemperature and pressure. Suitable acidic catalysts for thealdehyde-alcohol reaction to produce the acetals for cracking includephosphoric acid, toluene-sulfonic acid,

A convenient way of separating the 3,4-dienals formed according to theprocess of my invention is by extraction with a hydrocarbon solvent suchas hexane or heptane.

My invention is illustrated but not limited by the following examples. a.7

j V 7 Example, 1

Acetaldehyde dipropargyl acetal was prepared'by reacting paraldehyde andpropargyl alcohol using p-toluenesulfonic acid as catalyst. Theequilibrium mixture was neutralized and fractionated to' recover theacetal, n 1.4460. Propionaldehyde and isobutyraldehyde acetals and otheracetals of acetylenic alcohols were prepared and isolated in the samemanner.

Example 2 Acetaldehyde dipropargyl acetal was passed over a molybdenumoxide M 0 30-60 mesh catalyst for a contact time of 2 seconds at 300 C.The products were an- I alyzed. Fifteen percent by weight (approximately1 mole) of the starting acetaldehyde dipropargyl acetal had reacted toform yields of products as follows:

0.27 mole vinyl propargyl ether 0.52 mole 3,4-pentadienal 0.85 molepropargyl alcohol The identity of the vinyl propargyl ether,3,4-pentadienal, and also of 2,2-diernthyl-3,4-pentadienal was confirmedby use of a spectrograph and by infrared analysis, the

of the 3,4-diena1s being shown by a strong absorption at 5.1 microns. V

Example 3 dipropargyl acetal, B.P. 123 C., 11 1.4462-69, was passed overa molybdenumoxide catalyst at 275 C. with .46 seconds contact time toproduce '2-methyl-3,4-penta-' dienaldehyde, B.P. 50-54 C. at 100mm.pressure, in 15% conversion; As the contact time and/or temperature wasincreased, increasing amountsof the 3,4-dienaldehyde isomerized to theconjugated 2-methyl-2,4-pentadi enaldehyde, B.P. 75 80 Cat 100 mm.pressure.

Example 4 actually cracked to form the dienal and byproducts. The termmoles when used to refer to the products formed means in each case molesper mole of acetal starting material actually converted'to the products.

Following the procedure of Example 2 propionaldehyde .Isobutyraldehydedipropargyl acetal was passed over a molybdenum oxide catalyst atvarious temperatures ranging from.260320 C. according'to the'procedureof Example 2. At 320 C. and a contact time of 2 seconds completedecomposition of the acetal occurred (100% conversion) to give 0.82 mole2,2-dimethyl-j3,4-pentadi 'enal, 0.76 mole propargyl alcohol, about 0.6'mole is obutenyl propargyl ether and the remainder'of isobutyraldehydeand other low boilers. At 260 C. with 43% conversion the yield of2,2-dimethyl-3,4-pentadienal was over 0.90mole, with propargyl alcoholagain being somewhat lower. The identity of the2,2-dimethyl-3,4-pentadienal was confirmed by mass spectroscopicanalysis, infrared absorption, and a B.P. determination (B.P.=132 C.).

Example 5 Propionaldehyde 'dipropargyl acetal was passed over a catalystcontaining 20% by weight of said catalyst of silver and zinc in a 1:1ratiosupported on active carbon (prepared by decomposing a mixture oftheir oxalate salts) at 350 C. with a contact time of less than 60secends. The products were condensed and analyzed to recover propargylalcohol, unreacted acetal, and a 12% c011 version to2-methyl-3,4-pentadienaldehyde and isomers thereof. Similarly, with acopper-zinc catalyst, an 8% conversion was obtained. In the precedingexamples, percent conversion refers to the percent by weight of theacetal starting material areselected from the group consisting ofhydrogenand The 3,4-dienals prepared according to the pro cess of thisinvention may be,used as intermediates for isomeriza- 'tion to theconjugated dienaldehydes or partial hydrogenation to the 3- or4-olefinic aldehydes. Other usesare described in my above-mentionedco-pending application Serial No. 75,475.

Although the'invention has been described in considerable detail withparticular reference to certain preferred embodiments thereof,variations and modifications can be elfected within the spirit and scopeof the invention as. described hereinabove, and as defined .in theappended claims.

I claim:

1. A process for the preparation of dienals which 'c'omprises crackingin the vapor phase at 200 C. to 400" C., in the presence of a'solidmetal-containingcra'cking' catalyst and for a contact time up to aboutone minute,.an acetylenic alcohol acetal of the formula:

and collecting a dienal of the formulai v I 7 wherein R R R R and R areselected ironithe group consisting ofhydrogen and lower alkyl andwherein R 1 and R together'with the carbon atom to which'they' areattached form a saturated carbocyclic ring selected from the groupconsisting of a saturated carbocyclic hydrocarbon ring having 5 carbonatoms and a saturated carbocyclic hydrocarbon ring having 6 carbonatoms.

2. The process according to claim 1 wherein the catalyst comprisesmolybdenum oxide. v

3. The process according to claim 1 wherein the cracking in the vaporphase is accomplished at a temperature of from about 250 C. to 350 C. 4.The process according to claim 1 wherein the pressure at which thecracking is accomplished is not greater than 100 p.s.ilg.

5. A process for the preparation of dienals which cont prises contactinga propargyl alcohol acetal oi'an alde hyde of the formula, R R CHCHO,wherein R1 and R? lower alkyl, in gaseous form with a catalyst from. thegroup consisting of metals of groups I and II of the periodic tablehaving anatomic number of at 1east'29 metals.

of groups V through V111 of the periodic table andoxides, salts andmetal complexes of suchmetals at a temperature of from 200 C. to 400. C.anda pressure offup to 100 p.s.i.g. for no. longer than one minuteandcollecting the dienal formed. 6; The process according to claim 5wherein the temperature is from about 250 C. to about 350 C., the pressure about atmospheric and'the contact time from about 1 to about 10seconds.

7. The process according to claim 5 wherein the catalyst a comprisesmolybdenum oxide.

8. The process according to claim 5 wherein the acetal is acetaldehydedipropargyl acetal and the 3,4-,dienal collected 3,4-pentadienal.

9. The process according to claim 5 wherein the a ectal 3,189,655 5 6 ispropionaldehyde dipropargyl acetal and the 3,4-dienal OTHER REFERENCEScollected Z-methyl-3,4-pentadiena1. d 3 5 10. The process according toclaim 5 wherein the acetal an leser Orgamc Chemistry rd edl 19 isisobutyraldehyde dipropargyl acetal and the 3,4-dienal confidedlzdimethybs,ZLPentadienaL leser and Fleser, Advanced Orgamc Chemlstry,pp.

5 996-997. References Cited by the Examiner ppPiggzanggl: AcetyleneHomologs and Derivatives, 1950,

UNITED STATES PATENTS 2 5 3 325 3 51 Fahnoe 2 15 LEON ZITVER, PrimaryExaminer- 2,759,979 8/56 Hagemeyer et a1. 260-601 10 CHARLES PARKER, x ir,

2,947,786 8/60 Brannock 260601 UNITED STATES PATENT OFFICE CERTIFICATEOF CORRECTION Patent No. 3,189,655 June 15, 1965 Benjamin Thompson It ishereby certified that error appears in the above numbered patentrequiring correction and that the said Letters Patent should read ascorrected below.

In the grant, lines 1 to 3, for "Benjamin Thompson, of Kingsport,Tennessee," read Benjamin Thompson, of Kingsport, Tennessee, assignor toEastman Kodak Company, of Rochester, New York, a corporation of NewJersey, line 12, for "Benjamin Thompson, his heirs" read Eastman KodakCompany, its successors in the heading to the printed specification,line 3, for "Benjamin Thompson, Box 511, Kingsport, Tenn." read BenjaminThompson, Kingsport, Tenn. assignor to Eastman Kodak Company, Rochester,N. Y. a corporation of New Jersey i z i Signed and sealed this 18th dayof January 1966.

(SEAL) Attest:

ERNEST W. SWIDER EDWARD J. BRENNER Attesting Officer Commissioner ofPatents

1. A PROCESS FOR THE PREPARATION OF DIENALS WHICH COMPRISES CRACKING INTHE VAPOR PHASE AT 200*C. TO 400*C., IN THE PRESENCE OF A SOLIDMETAL-CONTAINING CRACKING CATALYST AND FOR A CONTACT TIME UP TO ABOUTONE MINUTE, AN ACETYLENIC ALCOHOL ACETAL OF THE FORMULA: